Renewable wave power

The ocean and waves are a powerful force to reckon with—I cannot count the number of times I have been slammed and tumbled by a strong wave at the beach. I’m sure many of you have had similar experiences.

Evidently, one must have respect for the power of the ocean but instead of just respecting this power, what about harnessing it as a form of renewable energy?

Waves after all, whether they be light waves, sound waves or ocean waves, are ultimately an oscillation that transfers or propagates energy without transferring mass.

So, to generate electricity from ocean waves humans need only convert the wave’s energy into mechanical energy to drive an electric generator—this is the fundamental concept behind wave energy converters.

One such type of wave energy converter is the pelamis wave energy converter which ‘rides’ the waves to generate electricity and resembles a semi-submerged ‘snake’ made from cylindrical segments joined together by hinges.

Segments of the pelamis will rise when the crest of the wave approaches, while segments will fall with the trough of a wave.

This relative motion between the segments causes the hinged joints between sections to move, converting the wave’s energy into the mechanical energy of the hinges which then drives an electric generator to produce electricity.

Electricity produced by the Pelamis is fed to a power cable along the seabed and back to land where the electricity can be used.

Cleverly, the pelamis’ sleek design ensures its survivability in rough ocean conditions, allowing it to effectively dive under wave crests when the waves become too large and too powerful for it to cope with.[1]

Another type of wave energy converter with a simplistic, robust design is the oscillating water column.

This is a partially submerged chamber with two openings – one below the waterline and one above the waterline with a turbine.  

As a wave approaches, water enters the column via the submerged opening and is pushed upward, increasing the pressure on the air in the chamber.

The air is pushed out of the column to the atmosphere via the turbine, causing it to rotate and drive an electric generator to produce electricity.

When the wave passes, water will leave the chamber reducing the pressure, causing air to be drawn into the chamber via the turbine, making it rotate and drive an electric generator to produce electricity.

The same principle is again at play: the conversion of the wave’s energy to mechanical energy—by turning a turbine through changes in air pressure induced by the wave—to produce electricity via an electric generator.

The oscillating water column’s simple design and robustness and survivability owing to its lack of moving parts below the water make it a promising wave energy converter design.[2][3]

Wave energy converters could very well supply more of our electricity in the not-too-distant future, with CSIRO’s research finding that “wave energy could contribute up to 11 per cent of Australia’s energy (enough to power a city the size of Melbourne) by 2050, making it a strong contender in Australia’s renewable energy mix”.[4]

Using renewable wave energy to produce electricity is just one of many examples of how science can help humans work towards sustainable development.